Catalyst stripping in a baffled vertical vessel

ABSTRACT

IMPROVED GAS-SOLID CONTACT IS ACHIEVED WHEN TREATING FINELY DIVIDED SOLIDS WITH A GAS IN A VERTICAL CYLINDRICAL VESSEL PROVIDED WITH A PLURALITY OF VERTICALLY-SPACED, DOWNWARDLY SLOPING BAFFLES AND WITH A SUBSTANTIALLY VERTICAL IMPINGEMET PLATE MOUNTED DIRECTLY ABOVE A DOWNWARDLY SLOPING BAFFLE. THE APPARATUS IS PARTICULARLY SUITABLE FOR STRIPPING RESIDUAL HYDROCARBONS FROM CATALYST USED IN FLUID CATALYTIC CRACKING PROCESSES.

April 17, 1973 ca. w. 5; MCDONALD 3,7

I CATALYST STRIPPING IN A BAFFLED VERTICAL VESSEL 7 Filed July 1, 1970INVENTQR GERALD W. a MC DONALD ATTORNEY United States Patent Olhce3,728,239 Patented Apr. 17, 1973 3,728,239 CATALYST STRIPPING IN ABAFFLED VERTICAL VESSEL Gerald W. G. McDonald, Summit, N.J., assignor toCommonwealth Oil Refining Company, Inc., New York, N.Y.

Filed July 1, 1970, Ser. No. 51,491 Int. Cl. B01j 11/02; Cg 13/14 U.S.Cl. 208-150 2 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THEINVENTION In fluid catalytic cracking a charge stock is contacted with afluidized catalyst under process conditions such that a substantialportion of the charge stock is transformed into desirable hydrocarbonproducts such as gasoline, olefin-rich light hydrocarbon streams, middledistillate blending stocks, and the like. The spent cracking catalyst isnormally regenerated and returned to the fluidized bed reactor forfurther use. However, prior to regeneration it is desirable to remove orstrip residual hydrocarbons from the spent catalyst. Normally strippingis carried out in a so-called stripper, which is an elongated vesselprovided with side-to-side interior baflies. The spent catalyst iscascaded downwardly over the stripper batfles while steam flowingcountercurrently to the descending catalyst contacts the same andremoves volatilizable carbonaceous materials therefrom. However, wherethe catalyst is very finely divided, for example, having a particle sizeof less than about 100 microns, it is extremely difficult to disperseefliciently steam or any other stripping fluid throughout the descendingcatalyst mass. It is an object of the present invention to provideapparatus and method which obviates the foregoing difficulty and whichprovide improved gassolid contact when finely divided solids are treatedwith a gas. Still other objects will readily present themselves to oneskilled in the art upon reference to the ensuing specification, thedrawings, and the claims.

. SUMMARY OF THE INVENTION The present invention contemplates anapparatus which comprises an elongated, vertically-disposed,substantially cylindrical vessel having a plurality ofdownwardly-sloping, vertically spaced baflles mounted therewithin, and asub stantially vertical impingement plate or plates mounted directlyabove a downwardly sloping, baflle so that a downwardly cascading solidparticle mass impinges against the plate or plates.

The herein contemplated improved stripping method comprises alternatelyexpanding and compacting a flowing spent catalyst mass within anatmosphere of a suitable stripping medium.

BRIEF DESCRIPTION OF THE DRAWING In the drawing,

FIG. 1 is an elevational view, partly in section, of a vessel embodyingthe present invention;

FIG. 2 is a perspective view of a bafile and a perforated impingementplate mounted thereon;

FIG. 3 is a perspective view of a baflle and a plurality of pairs ofimpingement plates mounted on the baflle and fixedly joined at an acuteangle relative to each other;

FIG. 4 is a perspective view of a baffle having a pinrality oftransversely-spaced impingement plates mounted thereon;

FIG. 5 is a perspective view of a baffle having a transversely extendingimpingement plate mounted above the baflle; and

FIG. 6 is a perspective view of a bafl le having a plurality oftransversely spaced impingement plates mounted thereon at an acute anglerelative to each other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, avertical, elongated, substantially cylindrical vessel 10 is providedwith downwardly-sloping baflles 11, which preferably overlap oneanother. Directly above a baflle 11 is situated an impingement plate 12which can be mounted on the side of vessel 10 as shown or on baflle 11itself as will be more fully discussed hereinbelow. Finely dividedsolids such as a spent catalyst, for example, enter the vessel throughan appropriate inlet opening 13 and cascade downwardly on baflle 11 andat the same time impinging on impingement plates 12 which temporarilyhold up and compact the impinging flowing mass and then disperse andexpand the flowing mass over the sides thereof. An appropriate inlet 14for a gaseous stripping medium such as a steam is provided at a lowerportion of vessel 10 and the stripping medium introduced therethrough isdispersed within vessel 10 by means of an appropriate manifold andascends upwardly through the cascading solid mass. The stripping mediumtogether with the volatile hydrocarbons or the like removed from thesolid mass can exit through opening 13, or an alternate outlet meanstherefor can be provided in the upper portion of vessel 10, if desired.Outlet means 15 situated at or near the bottom of vessel 10 is adaptedfor the removal of the treated solid mass.

The configuration of the impingement plate can vary. As shown in FIG. 2,perforated plate 16 is mounted directly on balfle 17. Temporaryretention and compaction of the flowing solid mass is readily achievedin this manner, yet a substantial buildup of solids behind plate 16 isavoided inasmuch as perforations 18 are sufliciently large to permitpassage of the flowing solids therethrough. Perforations 18 can bestraight-through openings or can be tapered, as desired.

A further embodiment of this invention is shown in FIG. 3 where pairs ofimpingement plates 19 and 20, 21 and 22, and 23 and 24 are mounted onbaffle 25. The pairs of plates can be readily manufactured from segmentsof a suitable angle iron and welded on baflle 25 in a transverselyspaced relationship or in any other configuration so as to generate thedesired alternate compaction and expansion of the flowing solids mass.

Similarly, FIG. 4 shows a series of spaced impingement plates 26, 27,and 28 and also 26', 27' and 28, extending transversely across baffle29, FIG. 5 shows a single impingement plate 30 mounted above baflle 31by means of suitable support such as rods 32 and 33, and FIG. 6 shows aseries of plates 34, 35, 36 and 37 mounted on bafl le 38 and at an acuteangle relative to each other so as to alternately constrict and expandthe solids mass flowing across baflle 38.

It has been found that in stripping a mass of spent fluid catalyticcracking catalyst the stripping efliciency is substantially improved ifthe catalyst mass is alternately compacted and expanded while surroundedby the striping that the temperature in the regenerator duringregeneration of the stripped catalyst is reduced.

While the present apparatus lends itself admirably to use in strippingof spent catalyst employed in hydrocarbon processing such assilica-alumina, platinum-alumina, molybdenum oxide-alumina, and thelike, the present apparatus is equally well suited for other processeswhich require an intimate contact of comminuted or powdered solids witha reactive, a drying, or a scrubbing gas. Typical such applications arein treating metal oxides with hydracids, hydrogenation, smelting ofsulfides, ore reduction, dehydration, drying of solids, and the like.

The foregoing discussion is intended as illustrative but not limiting.Still other variations and arrangements of parts within the spirit andscope of the present invention will readily present themselves to oneskilled in the art.

What is claimed is:

1. A method for strippng spent fluid catalytic cracking catalyst whichcomprises flowing a solid catalyst mass over a plurality of downwardlysloping baflies and impinging said catalyst mass onto a substantiallyvertical plate situated directly above at least one of the downwardlysloping bafiies and in the flow path of said catalyst mass, therebyalternately compacting and expanding said catalyst mass; said catalystmass flowing downwardly against an ascending stream of a gaseousstripping medium.

2. The method in accordance with claim 1 wherein the stripping medium issteam.

References Cited UNITED STATES PATENTS PATRICK P. GARVIN, PrimaryExaminer P. E. KONOPKA, Assistant Examiner US. Cl. X.R.

23-288 B, 288 G; 34-57 R, 171; 252-411, 420; 263 21 A; 266-2O

